The present invention relates generally to the field of pipe connections, and more particularly, is directed to an improved bell and spigot joint including a bent bell end for retaining a gasket within a circular groove.
It is presently the usual practice to extrude plastic pipes in elongate, cylindrical configuration of a desired diameter and then to cut the extruded product into individual lengths of convenient size suitable for handling, shipping and installing, for example, ten foot lengths or twenty foot lengths. Each length of pipe is enlarged or "belled" at one end sufficiently to join the next adjacent pipe section by receiving therewithin the unenlarged or "spigot" end of the adjacent length of pipe. The inside diameter of the bell is formed sufficiently large to receive the spigot end of the next section of pipe with sufficient clearance to allow the application of packing, caulking, gaskets or other devices designed to prevent leakage at the pipe joints when a plurality of pipe lengths are joined to form a pipe line. Depending upon the intended pressure of the fluid being conveyed, and other design parameters, the seal between adjacent lengths of pipe will be required to be more or less sophisticated.
Prior workers in the art, particularly in the plastic pipe industry, have developed various gaskets of suitable design to be retained within an internal groove formed in the bell. The gaskets were configured and designed to permit the pipe joint to be easily and rapidly made and to prevent leakage upon completion of the system. While experience has proved that the use of a formed gasket seated within an annular recess or groove which had been formed in the bell of a pipe is an efficient and suitable construction for sealing the joints between adjacent lengths of plastic pipe, prior workers have encountered difficulties in maintaining the seal under pressure or vacuum conditions. As operating pressures increase, the difficulties encountered in providing efficient and reliable seals have also increased.
In an effort to solve the sealing problems in pressure or vacuum piping systems, prior workers have developed gaskets of the type including extending lips to press against the spigot end. Additionally, other workers have provided gaskets having an internal peripheral groove within which is seated a locking ring to prevent movement of the seal and to discourage gasket blowout when the system pressure was applied. In a further effort to prevent unseating of the gasket when the pipe joint was made up or to prevent gasket blowout under severe conditions of use, efforts have been made to lock the gasket within the annular groove in the bell. Such efforts by prior workers in the art have included machining the groove to an angular configuration to firmly seat the gasket in the groove. Other workers have attempted to lock the gasket in the groove by applying, either by a threaded connection or by an adhesive juncture, an outer locking ring or retainer of smaller diameter than the gasket itself. Such prior art attempts to retain the gasket within the groove have proved to be only modestly successful and the end results have not justified the increase in manufacturing costs. Despite such efforts by the prior workers in the art, the need still remains to provide an efficient, trouble free and inexpensive sealing system that is highly reliable when in use with pressurized or vacuum applications.